u/Realistic-Slide-243

My 2016 Malibu push start just started doing this yesterday but a little under a year I’ve owned it it always was 14-14.1v but yesterday it would gradually drop to 12.8-13v while driving in the freeway and at a stop it turned off on the freeway. It’s not auto start but I could turn on right away and today it stays around 13.7-13.8. What could it be?